A conventionally proposed plasma ignition device includes a DC power supply for generating DC power used to generate spark discharges, and an AC power supply for generating AC power used to generate AC plasma, and is configured such that the DC power and the AC power are coupled together and transmitted to a spark plug (refer to, for example, Patent Documents 1 and 2). In such a plasma ignition device, in order to restrain flow of DC power to the AC power supply, the AC power supply is electrically connected to the DC power supply and to the spark plug via a capacitor.